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Lecture 1 introduction TUS 2013

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Lecture 1 introduction TUS 2013

  1. 1. Superconductivity Tokyo University of Science Sept.-Oct.2013 Professor Allen Hermann Department of Physics University of Colorado Boulder, CO 80401 USA
  2. 2. Syllabus for “Superconductivity”, an 8 (1 1/2 hour) lecture series at Tokyo University of Science, 2013 Allen Hermann, Ph.D. Lecture 1. Introduction Discovery, history, and superconducting properties (zero resistance and flux expulsion) Type I and Type II superconductors Low Tc and High Tc Materials Course References
  3. 3. Lecture 2.Phenomenology: Superfluids and their properties Electrodynamics and the Magnetic Penetration Length The London Equations and magnetic effects Fluxoids
  4. 4. Lecture 3. Phenomenology: Ginsburg-Landau theory and the intermediate state •Landau Theory of Phase Transitions •Ginsburg-Landau Expansion •Coherence Length •The Ginsburg-Landau Equations •Abrikosov Lattice and Flux Pinning
  5. 5. Lecture 4. Microscopic Theory The 2-electron Problem Annihilation and Creation Operators Solution of the Schroedinger Equation Cooper Pairs The Many Electron Problem- BCS Theory Solution of the Many Particle Schroedinger Equation by the Bogoliubov- Valatin Transformation The BCS Energy Gap
  6. 6. Lecture 5. Josephson Effects Pair Tunneling and Weak Links SIS Josephson Junctions Superconducting Quantum Interference Devices (SQUIDs)
  7. 7. Lecture 6. Superconducting Materials and their structures Low Tc Metals and Alloys Organic superconductors High Tc materials: cuprates, borides, and AsFe superconductors
  8. 8. Lecture 7. The pseudogap •Hole Doping and the Phase Diagram •Strange Metals •Experimental Probes •Current Pseudogap Theories •Pseudogap in BEC?
  9. 9. Lecture 8. Applications and Devices Levitation Wire applications and Superconducting Magnets Flux Flow Issues in High Tc, High Jc Wire Electronic devices Using Josephson Junctions and SQUIDS Nanotechnology and Superconductivity
  10. 10. Lecture 1 Introduction • Discovery, history and superconducting properties (zero resistance, magnetic flux expulsion) • Type I and Type II superconductors • Low Tc and High Tc materials • Course references
  11. 11. TYPES OF SUPERCONDUCTORS There are two types of superconductors, Type I and Type II, according to their behaviour in a magnetic field superconducting state Type I superconductors are pure metals and alloys Type I normal state This transition is abrupt
  12. 12. Type II superconducting normal state is gradual
  13. 13. WHAT IS SUPERCONDUCTIVITY?? For some materials, the resistivity vanishes at some low temperature: they become superconducting. Superconductivity is the ability of certain materials to conduct electrical current with no resistance. Thus, superconductors can carry large amounts of current with little or no loss of energy. Type I superconductors: pure metals, have low critical field Type II superconductors: primarily of alloys or intermetallic compounds
  14. 14. High Temperature Superconductivity CuO2 plane Copper-oxide compounds 1986: J.G. Bednorz & K.A. Müller La2-xBaxCuO4 Tc =35 K AF SC T x TN Tc T* Doped antiferromagnetic Mott insulator under optimally over doped spin gap strange metal Tc up to 133K Schilling & Ott ‘93 Are they unconventional superconductors? Not ordinary metals! Generic Phase Diagram
  15. 15. Record TC versus Year Discovered 0 20 40 60 80 100 120 140 160 180 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 Year TC(K) Hg NbN Nb3Ge La-Ba-Cu-O La-Sr-Cu-O YBa2Cu3O7 Bi2Sr2Ca2Cu3O8 Tl-Ba-Ca-Cu-O HgBa2Ca2Cu2O8 HgBa2Ca2Cu2O8 Pressure 1986
  16. 16. Hg0.8Tl0.2Ba2Ca2Cu3O8.33 138 K (record-holder) HgBa2Ca2Cu3O8 133-135 K HgBa2CuO4+ 94-98 K Tl2Ba2Ca2Cu3O10 TlBa2Ca2Cu3O9+  TlBa2Ca3Cu4O11 127 K 123 K 112 K Ca1-xSrxCuO2 110 K Highest-Tc 4-element compound YBa2Cu3O7+  93 K La1.85Sr0.15CuO4 40 K La1.85Ba.15CuO4 35 K First HTS discovered - 1986 (Nd,Ce)2CuO4 35 K SOME HIGH Tc SUPERCONDUCTORS Chemical formula Tc
  17. 17. APPLICATIONS: Superconducting Magnetic Levitation The track are walls with a continuous series of vertical coils of wire mounted inside. The wire in these coils is not a superconductor. As the train passes each coil, the motion of the superconducting magnet on the train induces a current in these coils, making them electromagnets. The electromagnets on the train and outside produce forces that levitate the train and keep it centered above the track. In addition, a wave of electric current sweeps down these outside coils and propels the train forward. The Yamanashi MLX01MagLev Train
  18. 18. A superconductor displaying the MEISSNER EFFECT Superconductors have electronic and magnetic properties. That is, they have a negative susceptibility, and acquire a polarization OPPOSITE to an applied magnetic field. This is the reason that superconducting materials and magnets repel one another. If the temperature increases the sample will lose its superconductivity and the magnet cannot float on the superconductor.
  19. 19. 1. London theory - rigidity to macroscopic perturbations implies a “condensate” (1935,1950) 2. Ginzburg-Landau (Y) theory - order parameter for condensate (1950) 3. Isotope effect (Maxwell, Serin & Reynolds, Frohlich, 1950) 4. Cooper pairs (1956) 5. Bardeen-Cooper-Schrieffer (BCS) microscopic theory (1957) 6. Type-II superconductors (Abrikosov vortices, 1957) 7. Connection of BCS to Ginzburg-Landau (Gorkov, 1958) 8. Strong coupling superconductivity (Eliashberg, Nambu, Anderson, Schrieffer, Wilkins, Scalapino …, 1960-1963) 9. p-wave superfluidity in 3He (Osheroff, Richardson, Lee, 1972; Leggett, 1972) 10. Heavy Fermion Superconductivity (Steglich, 1979) 11. High Temperature Superconductivity (Bednorz & Muller, 1986) 12. Iron Arsenides (Hosono, 2008) A (Very) Short History of Superconductivity
  20. 20. Course references 1) Introduction to Superconductivity, M. Tinkham, McGraw Hill 1996 2) Principles of Superconductive Devices and Circuits, T. Van Duzer and C. W. Turner, Elsevier, 1981 3) Introduction to Solid state Physics, C. Kittel, Wiley, 1976 4) Superconductivity of Metals and Cuprates, J.R. Waldram, IoP, 1996 5) Many on-line sources including T. Orlando, B. Chapler, M. Rice, I. Guerts, M. Cross, N. Kopnin, and others

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